Insulator



H. B. SMITH Oct. 1, 1929.

INSULATOR Original Filed July 28, 1923 INVENTOR fia/"o/d B. Sm/f/VATTORNEY WITNESSES:

Patented Dot. 1, 1929 UNITED STATES PATENT OFFICE HAROLD B. SMITH, OFWORCESTER, MASSACHUSETTS, ASSIGNOR TO WESTINGHOUSE ELECTRIC &MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA INSULATORApplication filed 3 111128, 1923, Serial No.

My invention relates to insulators and particularly to insulatorsforsupporting the conductors of high-potential circuits.

One object of my invention is to provide an insulator, of the aboveindicated character, that shall embody a metal pin or supporting memberfrom which the electrostatic stresses are so withdrawn as to preventarcover thereto and thereby prevent injury to an insulating member onthe pin.

Another object of my invention is to provide an insulator comprisingterminal members that shall be constructed and related to so widelydistribute and definitely direct the electrostatic field as to permitthe use of a usual form of insulating member having a surface to whichthe field substantially conforms and around which a zone of maximumpotential gradient is disposed. in spaced relation thereto.

A further object of my invention is to provide a high-potentialinsulator that shall be simple and durable in construction, economicalto manufacture and effective in its operation.

In my copending application, Serial No. 548,818, Insulator, filed April1, 1922, is set forththe feature of simultaneously widely distributingand definitely directing the electrostatic field of an insulator to havea zone or portion of maximum potential gradient surrounding thelongitudinal axis of the insulator in spaced relation thereto and aweakened central or inner portion through which an insulating supportingpin or member extends. This construction, removes fracturing andcorona-forming stresses and disrupts arcs from the insulating member andutilizes entirely the dielectric strength of air to determine theultimate voltage limits of the insulator. In other words, there is anair path, for the maximum electrostatic stresses, which is not affectedby electrostatic field-disturbing objects, wet oreepage surfaces andother elements which frequently have caused break down in ordinaryinsulators of the prior art.

However, it was discovered that the abovedescribed insulator could beimproved for o eration under wet conditions by the provision of arain-drip portion disposed outside 654,333. Renewed September 22, 1827.

the zone of maximum potential gradient. This feature is fully disclosedin my copending application, Serial No. 559,743, Insulator, filed May10, 1922.

The insulator of the latter application embodies both of theabove-described features in combination and is very effective under bothwet and dry conditions.

The above-described insulator or insulators, while comprehending certainbroad features, are more particularly adapted for operation with pins orsupporting members of insulating material. Accordingly, my presentinvention is an adaptation of the features thereof in an insulatoremploying a metal pin or supporting member. which, is desirable forcertain purposes within certain voltage values. Higher voltages may beadvisably employed with a pin insulator employing these principles thanhas been found practicable with previous insulators of the metal-pintype.

In practicing my invention, I provide a metal pin or supporting memberand an insulating member, both somewhat similar to insulators of theprior art but in which the insulating member is very materiallysimplified, in which the electrostatic field-distributing and directingfeature, of the first mentioned co-pending application, and the rain-'drip feature, of the second-mentioned copending application areembodied. This adaptation involves the reforming or redistribution of aportion of the electrostatic field, as well as changes in the distancesand relations between certain parts, to attain an insulator embodying orretaining certain desirable features of insulators of the prior art andto provide an insulator which is free from many of the objectionsincident thereto.

The single figure of the accompanying drawing is a view, partiall inside elevation and partially in section, 0 an insulator constructed inaccordance with my invention.

In general, the insulator comprises a supporting member or pin 1 that isadapted for mounting on a cross arm or other supporting structure 2, aninsulating member 3, an upper terminal member A an 1 lower terminal memr The pin 1, while preferably constructed entirely of metal, may beconstructed of menlating material having a conducting surface. Theinsulating member 3 is preferably constructed of refractory insulatingmaterial, such as porcelain or glass, and may comprise one member or aplurality of members joined by cement.

The upper terminal member 4, which may be constructed of insulatingmaterial having a conducting surface, is preferably constructed of sheetmetal to be of substantially hood shape having a cup or socket portion6, which is mounted on the insulating member 3 and secured thereto, asby a body of cement 7. The socket portion 6 may be provided with upperraised portions 8 between which a conductor 9 is disposed and secured inposition by a tie-wire 10 that is wound around the conductor 9 andaround the socket portion 6, in the usual manner, under an annular ribor flange 11 on the socket portion 6. However, a metal clamp or othersuitable means may be provided to hold the conductor 9 in position.

The member fl is further provided with a portion 12, adjacent to thesocket portion 6, which is shaped to cause the electrostatic fieldbetween the member 4 and the pin 1 to be of substantially bowl shape, towhich the outer surface of the insulating member 3 substantiallyconforms. This feature is more fully explained in Patent No. 1,374,998,Insulator, issued April 19, 1921, to C. L. Fortescue and G. I.Gilchrest, and assigned to the Westinghouse Electric & ManufacturingCompany.

An intermediate portion 14 of the member 4 surrounds the portion 12thereof and is downwardly relatively widely bowed, or curved, about arelativel long radius to be closer to the member 5 tian any other partthereof. In other words, the portion 14 provides a maximum potentialgradient adjacent to its surface surrounding the longitudinal axis ofthe insulator in spacedrelation to the insulating member 3.

The outer perimeter 15 of the member 4 constituting a water-dripportion, is so related to the member 5 that moisture, descending in thedirection of a dotted line A, shall be removed from the member 5 agreater distance than along a dotted line X Which represents theshortest distance and the field of maximum electrostatic intensitybetween the members 4 and 5.

The member 5 is of substantially ring shape and surround the pin 1, inrelatively Widely spaced relation thereto, and is of relatively largeradius in its dimension Y. This construction provides an annulus havinga top surface of relatively great curvature descending by relativelywidely curved surfaces on either side thereof, or in other words,joining the inner and outer perimeters of the ring 5 by a relativelywidely curved surfai The member 5 may be supported on the pin 1 byradially projecting arms 16 having relatively widely rounded surfaces toprevent the formation of corona and spaces therebetween to permitmoisture to descend from the upper parts of the insulator.

As above constructed, the members 4 and 5 very widely distribute theelectrostatic field therebetween and, at the same time, so definitelydirect the same as to provide a portion of maximum potential gradientsurrounding the longitudinal axis of the insulator in relatively widelyspaced relation to the insulator 3. The inner portion of theelectrostatic field, in which the pin 1 and the insulating member 3 aredisposed, is materially weaker than the zone adjacent to the line X. Theelectrostatic field in this weakened inner portion is further directed,or reformed, by the relation between the portion 12 of the member 4 andthe pin 1, to cause it to conform substantially to a preferred standardform of insulating member 3.

Further, the distance represented by the line X, is shorter than thedistance along the surface of the insulating member 3, between theportion 12 of the member 4 and the pin 1, and is shorter than thedistance between the member 5 and the water-drip portion 15. Thedistance represented by the line X is also shorter than the distancerepresented by the line A, between the support 2 and the waterdripportion 15. These relations ensure that ultimate breakdown will occuralways between the member 5 and the portion 14.

By means of my invention, a standard metal pin anda refractory or otherinsulating member, free of petticoats and thereby of simple form andeconomical to manufacture, are provided together with relatively simplemetal parts so shaped and related as to render the insulator verydurable in construction and effective in operation.

While T have shown and described a particular form of my invention,changes may be effected therein without departing from the spirit andscope thereof, as set forth in the appended claims.

I claim as my invention:

1. An insulator comprising terminal mem. bers constructed tosimultaneously widely distribute and definitely direct the electricfield thereof to have a portion of maximum potential gradientsurrounding an axis of the insulator, and a weakened portion inside saidportion, one of said members having a ortion projectin toward the otherto reorm a portion 0 said weakened portion of the field,-and aninsulating member having an end recess by which it is fitted over theend of said promoting terminal portion and an outer end portion on whichsaid other terminal member is mounted, said insulating memher alsohaving a side surface substantially IOI conforming to said reformedweakened portion.

2. An insulator comprising terminal members constructed tosimultaneously widely distribute and definitely direct the electricfield thereof to have a portion of maximum potential gradientsurrounding an axis of the insulator and a weakened portion inside saidportion, one of said members having a portion projecting toward theother and operating to reform a portion of said inside portion of thefield, and an insulating member mounted on said projecting portion andconforming to said reformed portion of the field.

3. An insulator comprising a terminal structure including a metal pinportion at one end, a second terminal structure at the other end of theinsulator for causing a portion of the electric field between said pinpor- 7 tion and the second terminal structure to assume a predeterminedsubstantially bowl shape, and an insulating member mountedon the pinportion for supporting said second terminal structure and having asurface conforming substantially to said field, said first and secondterminal structures also being constructed and related to each other andto the insulating member to simultaneously widely distribute anddefinitely direct another portion of the field to occupy a zone ofmaximum potential gradient surrounding the axis of the insulator inspaced relation to said insulating member.

4. In an insulator, the combination with a vertically disposed metal pinand an insulating member mounted on the upper end thereof, of a lowerterminalmember surrounding the pin in spaced relation thereto and havinginner and outer perimeters connected by a gradually curved surface, andan upper terminal member of substantially hood shape having' an outerwater-drip portion, an intermediate gradually curved portion surroundingthe axis of the insulator and an inner portion for directing the fieldrelative to said insulating member, the distance between portions of thegraduall curved portions of the terminal members being less than thedistance" from the lower terminal member to said water-drip portion andless than the distance from the upper terminal member to the pin alongthe surface of the insulating member.

5. A high-potential insulator comprising an insulating member havinglongitudinal surfaces interce ting lines parallel to the longitudinalaxis 0 the insulator, oppositel -disosed terminal structures thereforeac em- Eodying a widely-laterally-curved portion surrounding said axisin laterally-spaced relation thereto with the crest of said curvedportion advanced toward the crest of the other to provide a tube-likefield zone be- 1 tween the terminals in the portion of whichcorresponding to the wall of the tube the maximum field stresses of theinsulator occur and inside of which wall-like portion the terminals areformed to provide a weakened field region in which electrostatic linesextend substantially parallel to said axis, said terminal structuresalso embodying portions to direct certain of the lines in saidweakenedfield region to conform substantially to said tongitudinalsurfaces of the insulating mem- 6. A high-potential insulator comprisinga lower terminal structure including a metal pin, an insulating memberdisposed over one end of the pin, an upper terminal structure embodyingan intermediate annular ortion which, in co-operation with the pin,directs a portion of the field therebetween to conform substantially tothe longitudinal surface of said insulating member, said terminalstructures each also embodying an outer widelylaterally-curved ortionsurrounding the longitudinal axis 0? the insulator in laterallyspacedrelation to said insulating member and pin with the crest of said curvedportion advanced toward the corresponding portion of the other andadapted to provide a tube-like electrostatic field zone between theterminals in the portion of which corresponding to the wall of the tubethe maximum field stresses of the insulator exist.

7. An insulator comprising terminal members constructed to widelydistribute and definitely direct the electrostatic field thereof to havea zone of maximum potential gradient within a locus surroundin an axisthrough said members and a wee ened portion between said zone and saidaxis, one of said members including an element operating to reform aportion of said weakened field portion, and an insulating memberconforming to said reformed field portion supported by said element.

8. An insulator comprising terminal members constructed to widelydistribute and defi- 7.

nitely direct the electrostatic field thereof to have a zone of maximumpotential gradient within a locus surrounding an axis through saidmembers and a weakened portion between said zone and said axis, one ofsaid members having a portion projecting toward the other and operatingto reform a portion of said weakened field portion, and an insulatingmember having a ortion substantially conforming to said re ormed fieldportion and a ortion enclosing a portion of said projectmg portion. 1

n testimony whereof, I have hereunto subscribed my name this tenth dayof Jul 1923.

' HAROLD B. S TH.

